Field of the Invention
The invention relates to a tool head for a modular shank tool. The invention further relates to a shank tool comprising such a tool head and to a manufacturing method for the tool head.
Background Information
Tools for machine cutting of workpieces, in particular workpieces made of metallic materials, are occasionally used in high-volume production and manufacturing facilities. Machine cutting can basically be divided into two fields. One field is machine cutting with geometrically undefined cutters. Typical methods are here, for instance, grinding and lapping. The other field is machine cutting with geometrically defined cutters, such as, for example, drilling, milling and turning. In terms of the economy of production, the longest possible service life for the tools used is demanded in both fields. The service life of the tools is determined by various, mutually interacting factors. Specifically in the field of geometrically defined cutters, these factors are in part inherent to the particular tool, such as, for example, cutter geometry or tool material, which are both in turn also dependent on a material of the workpiece to be machined. Other factors are occasionally adjustable process conditions, such as, for example, a supply of a cooling lubricant and a cutting speed. Cooling lubricants, as the term implies, serve on the one hand to cool the tool, in particular the cutter, as well as a removed chip, and on the other hand to provide lubrication between the cutter and the workpiece. In addition, however, the cooling lubricants also take care of the evacuation of chips from a cutting zone.
For extremely hard or metallic workpiece materials, tools made of hard metal or tool inserts made of ceramic materials are normally used. In a multistage process, these materials are first pressed from granular raw materials or, in alternative methods, such as, for instance, powder injection molding, are converted into a preform (also “green compact”). This preform is then compressed in a sintering process and “baked” into a solid formed part. Because of the generally expensive high-precision tools, it has proved economic not to exchange the whole tool in the event of excessive wear, but only the heavily loaded, rapidly wearing cutters. For this, tool systems comprising exchangeable tool heads made from hard metals or ceramics are widely used.
Ducts for the supplying of cooling lubricant are occasionally integrated in the tools themselves close to the cutting zone. This is advantageous, in particular, for machine-cutting methods in lower lying workpiece regions, such as, for instance, in bores, since an external cooling lubricant supply at the bottom of the bore is made difficult by the tool itself and the externally supplied cooling lubricant, as it flows into the bore, forces the chips back into the cutting zone.
A simple embodiment of an integrated cooling lubricant supply of this kind is a central bore which runs in the longitudinal axis through the whole of the tool. An improved cooling lubricant supply is achieved, for instance, by two ducts which emerge on the flanks of the tool tip. These ducts are occasionally produced by extrusion methods helically along a spiral of chip grooves of the tools.
For the cooling lubricant supply, complex shapes of the discharge openings and of the ducts for the cooling lubricant are often advantageous in terms of the flow and flow rate of the cooling lubricant and the cooling of the engaging cutters. Disadvantageously, these complex duct structures represent a not insignificant obstacle for the production of the aforementioned hard material tools. Undercuts and complex inner hollow structures can be realized only with increased production complexity. Suitable methods are found, for instance, in the field of so-called Rapid Prototyping or Rapid Tooling methods, in which components are made layer by layer in time-consuming processes, for example from powders.
A tool tip having two openings for the cooling lubricant is known, for instance, from U.S. Pat. No. 3,085,453. There a one-piece tool tip is defined, which is first pressed in a powder-metallurgical method and is then compacted in a sintering process and brought into the final form. The cooling lubricant openings are shaped during the pressing of the powder by a core element in the pressing mold. Next the sintered tool tip is soldered onto a tool shank. A drawback with this method is that only straight ducts for the cooling lubricant can be produced, since no other structures can be formed by the core element in the pressing mold. Otherwise, the core element would no longer be able to be removed from the mold.
A further tool tip, defined in U.S. Pat. No. 6,551,035, likewise comprises ducts for cooling lubricant and is formed from two different materials. The aim of the different materials is to match the cutters of the tool tip to different load intensities. The outer cutter regions are formed from a harder material, since there, due to the higher cutting speed in the case of a rotary tool, greater hardness leads to lower wear. This tool tip is formed in a multi-component injection molding process and is then sintered. That is to say, the two different materials are preformed in a process into a coherent component and are then sintered, whereupon the two materials respectively form a core and a mantle. As in the aforementioned document, the ducts for the cooling lubricant are likewise jointly formed in the injection molding process.
Further known cutter inserts for drilling or milling tools are known, for instance, from U.S. Pat. Nos. 3,422,706; 6,663,326 and U.S. 2010/0021253.